It is known to provide a valve train or valve actuator assembly for an engine such as an internal combustion engine of a vehicle such as a motor vehicle. Typically, the valve train includes one or more valves, a cam shaft having at one or more cams, and a tappet contacting each cam and valve. Typically, engine valve actuation is accomplished via the engine-driven camshaft. However, this type of valve actuation introduces constraints on valve operation that preclude optimal valve opening and closing schedules, compromising engine performance, fuel economy, and emissions.
It is also known to provide a camless valve train for an internal combustion engine. An example of such a camless valve train is disclosed in the prior art. For example, a camless intake/exhaust valve for an internal combustion engine is controlled by a solenoid actuated fluid control valve. The control valve has a pair of solenoids that move a spool. The solenoids are digitally latched by short digital pulses provided by a microcontroller.
One disadvantage of some camless valve trains is their poor controllability due to open loop instability, which causes great difficulty in their operation. Another disadvantage of some camless valve trains is that they do not provide full capability for variable lift. Further disadvantages of some camless valve trains are that they have relatively high cost, large size, high energy consumption, low repeatability from cycle to cycle and cylinder to cylinder, hard seating impact, and high seating velocity induced noise.
As a result, it is desirable to provide a valve actuator assembly for an engine that improves controllability. It is also desirable to provide a valve actuator assembly for an engine having more flexibility and full capacity for variable lift. It is further desirable to provide a valve actuator assembly for an engine that reduces energy consumption and provides satisfactory seating velocity. Therefore, there is a need in the art to provide a valve actuator assembly for an engine that meets these desires.